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Facial feature extraction method and apparatus for a neural network acoustic and visual speech recognition system

  • US 5,680,481 A
  • Filed: 06/09/1995
  • Issued: 10/21/1997
  • Est. Priority Date: 05/26/1992
  • Status: Expired due to Fees
First Claim
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1. A method for extracting a visual feature vector from a sequence of images, each having a plurality of horizontal raster lines, of frontal views of a speaker'"'"'s face in a speech classification system, the method comprising the following steps:

  • a) sampling and quantizing each image at uniform intervals along each horizontal raster line of the image to produce an image represented by an array of pixels, each pixel value representing gray-scale level;

    b) preconditioning the pixel image by spatially smoothing and enhancing edges separating regions of greater and less gray-scale intensity using spatial convolution techniques;

    c) thresholding the preconditioned pixel image by using a threshold value for determining a left eye area, a right eye area, and a mouth area, wherein the threshold value is used to define each of the left eye area, the right eye area, and the mouth area;

    d) calculating a left eye area location, a right eye area location, and a mouth area location from the left eye area, the right eye area, and the mouth area, respectively;

    e) establishing an eye line segment as a straight line connecting the left and right eye area locations;

    f) establishing a vertical axis of symmetry as a straight line that is perpendicular to and bisects the eye line segment connecting the left and right eye area locations;

    g) establishing a mouth line by passing a straight line through the mouth area location, the mouth line being perpendicular to the vertical axis of symmetry;

    h) selecting image pixels along the axis of symmetry in the vicinity of the mouth line to form a vertical sectional view of gray-scale pixel values;

    i) selecting image pixels along the mouth line in the vicinity of the axis of symmetry to form a horizontal sectional view of gray-scale values; and

    j) selecting a set of pixels and associated pixel values that occur at the peaks and valleys (maximas and minimas) of the vertical and the horizontal gray-scale pixel value sectional views as a set of elements of a visual feature vector.

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